How can I typeset Greek letters in siunitx?

Question

I want to use a Greek letter as the variable with the unit, and I am using siunitx to do it. The code below cannot be successfully compiled in pdflatex

\documentclass{article}
\usepackage{siunitx}
\begin{document}
\SI{\alpha}{\radian}
\end{document}

How can I typeset the Greek letter in siunitx?

Answer 1

You need to disable the parser for anything that is not a number:

\documentclass{article}
\usepackage{siunitx}
\begin{document}
\SI[parse-numbers = false]{\alpha}{\radian}
\end{document}